Method for the production of a nonfrilled metal strip from metal powder



Jan. 26, 1960 .BOUGHTON ETAL 2,922,223

METHOD FOR THE PRODUCTION OF A NON-FRILLED ME STRIP FROM METAL POWDER 2Sheets-Sheet 1 Filed Dec. 11. 1956 Jan. 26, 1960 Filed D60. 11, 1956 A.R. BOUGHTON ETAL 2,922,223 METHOD FOR THE PRODUCTION OF A NON-FRILLEDMETAL STRIP FROM METAL POWDER 2 Sheets-Sheet 2 FIG. 3

ARTHUR REGINALD BOUGHTON DAVID KENNETH WORN INVENTOR.

BY MK ATTORNEY NIETHOD FOR THE PRODUCTION OF A NON- FRILLED METAL STRIPFROM METAL POWDER Arthur Reginald Boughton, Northfield, Birmingham, and

David Kenneth Worn, Hall Green, Birmingham, England, assignors to TheInternational Nickel Company, Inc., New York, N.Y., a corporation ofDelaware Application December 11, 1956, Serial No. 627,662-

Claims priority, application Great Britain December 15, 1955 3 Claims.(Cl. 29-4205) The present invention is directed to a method forproducing metal strip by the direct compression or compacting of metalpowder and more particularly to a method for the direct rolling of metalpowder to fiat strip having a width in excess of about one inch andbeing free of frilling along the edges.

It is known to form metal strip from metal powder by a series of steps.In the first step, the powder is fed between a pair of horizontalcylindrical rolls, with their axes arranged in a plane which may forexample be horizontal, which compact the powder into a continuous striphaving sufficient mechanical strength to withstand a limited amount offurther handling. The compacted strip is next sintered by passagethrough a furnace at a high temperature and the sintered strip, which isstill porous, is then subjected to a series of cold rolling operations,with intermediate annealing stages, to reduce it to a dense, non-porousstrip.

In the first step, the powder has hitherto been fed from a hopperdirectly into the roll gap, or alternatively onto one roll, which as itrevolves carries the powder into the roll gap as a layer uniform inthickness throughout its'width. These methods give satisfactory resultsin making narrow strip with a width of up to about one inch. As thewidth of the strip produced is increased, for example, to about sixinches, it is found that the edges of the strip tend to form into frillsto an increasing extent in the course of subsequent cold rolling. Thiseffect is aggravated if, in order to avoid contamination of the porousmaterial by lubricant, the cold rolling is carried out usingunlubricated rolls. Further attempts to cold roll such frilled striponly lead to very severe distortion and even splitting of the strip, andno convenient way of restoring it to the desired flat state is known.

It is an object of the present invention to provide a method for rollingmetal powder to fiat metal strip having a width in excess of about oneinch and being free of frilling along the edges.

Another object of the invention is to provide a method for directlycompacting metal powder into metal strip exceeding about one inch inwidth such that the resulting compacted strip can be brought to asubstantially non-porous state by cold rolling and annealing whileremaining fiat and being free of frilling along the edges.

Other objects and advantages of the invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawing in which:

Figure 1 depicts an elevation of a rolling mill adapted to roll metalpowder into metal strip and having powder feeding meanscontemplated inaccordance with the invention; a

Fig. 2 depicts a plan view of the apparatus shown in elevation in Fig.1; and

. Fig. 3 ,depictsa schematic representation for carrying outthe" process.of the present invention for rolling metal powder into metal stripwhich is free from frilling along the edges.

According to this invention, frilling of the edges of 2,922,223 PatentedJan. 26, 1950 the strip is eliminated or reduced by feeding the powderto the compacting rolls so that the amount delivered to the'rolls toform the center of the strip is greater than that at the sides.

Preferably, the powder to be compacted, e.g., rolled, in accordance withthe invention is fed to the compacting rolls through a gap which isrelatively wider in the region of the center of the rolls than'in theregion of the roll edges such that powder feeding through the gap isformed into a layer which has a cross-section which is relativelythicker at the center than at the edges and the powder layer having thesaid cross-section is then fed into the rolls. We have found that whenthe conventional uniform feed of powder is used the powder tends to beforced from'the center to the sides of the rolls during the initialcompacting, giving rise to a band of metal of higher density along eachedge of the strip. As soon as the porosity of the strip has been reducedby cold rolling to such an extent that the effect of the cold work is toelongate the metal strip as well as to eliminate porosity, thediiference in density across the width of the strip leads todifferential elongation of the center and edge zones which shows itselfas frilling of the edges. The extra initial supply of powder in thecenter of the strip compensates for this tendency for the powder to beforced outwards during compacting and avoids the formation of zones ofhigh density along the edges of the strip.

The rolls commonly used in. cold strip mills in the breaking-down stagesare slightly cambered. When such rolls are used it is preferred tosupply such an excess of powder to the center of the strip that thespreading effect of the compacting rolls is slightly overcompensated andthere is a zone of higher density along the center of the strip in theearly stages of cold rolling. When the cold rolling takes place thecambered rolls spread the metal outwards from the central zone of higherdensity and a flat product is obtained at the end of the series of coldrolling operations. In the case of compacting rolls arranged in the samehorizontal or near horizontal plane, the invention may-be carried out bycontrolling the thickness of the layer of powder on the feed roll bymeans of a spreader plate so shaped that the gap between the edge of theplate and the roll surface is greater at the center than at the sides. Alayer of powder is thus formed having a thickness which decreasesprogressively from the center to each side. The spreader edge may, forexample, be concave in the form of an arc of a circle. The powder may befed to the roll from a hopper extending above the gap, and the spreaderplate may be mounted in the hopper and inclined to extendacross the gapnearly into contact with one roll as shown in Fig. 1 of the drawing. Theinclination of the plate may be adjustable to give easy means of varyingthe thickness of the layer as a whole.

We have found that the relative amounts of powder fed to the center andsides of the rolls to form a strip of a given thickness will vary withthe bulk density and flowing power of the powder used.

We have further found that the surface of the compacting rolls tends tobecome polished with use. The degree of polish may vary from side toside of the rolls. The amount of powder carried into the gap between agiven pair of rolls at a given point of their width and compacted theredecreases as the degree of polish of the rolls at that point increasesso that it may be necessary from time to time to adjust the relativeamounts of powder fed to the rolls at difierent points across theirwidth. All these variations can be compensated for by the use of a setof difierently shaped spread er plates but it is preferred to use aspreader plate in which the contour of the controlling edge isadjustable.

One form of apparatus contemplated'in accordance with the invention isdepicted in Figs. 1 and 2 wherein Fig. 1 depicts the section 11 of Fig.2. In the drawing, 1 and 2 are the compacting rolls, 3 is a hopper forholding powder to be rolled and 4 is a form of adjustable spreader plateThe spreader plate 4 consists of a number of narrow strips 6 of metal orother abrasionresistant material arranged side by side in a support 5 toform a pla'te'in which the lower ends of the strips define thecontrolling edge. The broken line 9 represents the element on the feedroll 1 which with the controlling edge of the spreader plate 4 forms agap which controls the cross-sectional form of the powder layer enteringthe compacting rolls. It will be seen that the gap is wider in theregion of the center of the roll than in the region of the roll edges.Each of strips 6 is longitudinally adjustable in the support. The stripsmay be slotted, the slots receiving screws 8 which enter the support andcan be tightened to hold the strips in position. Alternatively, thesupport may be slotted as shown at 10. Finer and more convenientadjustment can be obtained, however, by making each strip engage the endof a set-screw mounted to turn in the support and in so doing to movethe strip longitudinally.

Instead of feeding the powder onto only one of the rolls, it may be feddirect from the hopper into the roll gap, the flow being controlled by awedge supported above the roll gap. Again, powder may be fed onto boththe compacting rolls in two separate flows, each controlled by aspreader plate. This variation is useful if it is desired to form acomposite strip from two different metal powders. r

Fig. 3 depicts schematically the method for rolling metal powder intometal strip having a width of at least about one inch and which is freefrom frilling along the edges. As shown in Fig. 3, metal powder 12 isheld in hopper 3 and is fed to compacting rolls 1 and 2 between the gapdefined by spreader plate 4 and the surface of roll 1. As more fullyshown in Figs. 1 and 2, the gap between spreader plate 4 and the surfaceof roll 1 is greater in the region of the center of the roll than in theregion of the roll edges. Powder 12 is compacted by rolls 1 and 2 intocompacted strip 14, which is then sintered in sintering furnace 15. Thesintered strip is then cold rolled in rolls 16 and 16'7after which it isannealed in annealing furnace 17 and again cold rolled in rolls 18 and18'. Further successive stages of cold rolling with intermediateannealing may be employed. The dense, rolled strip, which is free fromfrilling along the edges, may be coiled on coiling drum 19.

As an example, in rolling a strip 5% inches wide from pure carbonylnickel powder using a pair ofcompacting rolls each twelve inches wideand eight inches in diameter starting with a uniform powder layer aboutoneeighth of an inch thick delivered to the compacting rolls and saidrolls having a roll gap such as to give a compacted strip 30/ 1000 of aninch thick, it was found that after sintering and two stages of coldrolling, with an intermediate annealing treatment, to give a totalreduction of /1000 of an inch, the strip issuing from the rolls wasbadly frilledat the edges. Attempts to restore the strip to flatness byannealing and further cold rolling only increased the buckling. When thepowder was delivered to therolls at the same rate but using a spreaderplate so shaped that the thickness of the powder layer increased in aseries of steps from zero at the sides to one-quarter inch at thecenter, it was found that using the same rolling speed a compactedstrip, also about 30/1000 of an inch thick, was obtained which aftersintering could be progressively cold rolled down in four stages to afully consolidated, non-porous strip with a. uniform thickness of 5/1000of an inch without any frilling or other distortion occurring.

It will be appreciated that in accordance with the invention metal stripcan be produced in any desired length since it is only necessary tocontinue feeding powder to the mill in order to produce the desiredamount of strip. Furthermore, it is to be pointed out that there is nonecessity for employingany sort of carrier strip for the purpose ofconducting the powder through the compacting rolls. The compacted powderemerging from the rolls has sufficient strength that it can be handledin subsequentjdesired annealing and/ or rolling operations designed toreduce the strip to a substantially compact, non-porous form.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

We claim: 7

1. The method for producing substantially flat, dense metal strip by thedirect rolling of metal powder which comprises feeding to compactingrolls a layer of uncompacted metal powder greater than about 1 inch inwidth, the cross section of said layer being relatively thicker towardthe center thereof and decreasing in thickness towards eachedge,.rolling said powder layer to compact said powder layer to metalstrip, sintering the resulting compacted metal strip, cold rolling andannealing the compacted and sintered metal strip to producesubstantially fiat, dense metal strip greater than about 1 inch in widthandbeing substantially free from frilling along the edges. a

2. The method for producing substantially fiat, dense metal strip by thedirect rolling of metal powder which comprises forming metal powder intoan uncompacted layer at least about 1 inch wide and having a crosssectional thickness relatively greater towards the center thereof anddecreasing in thickness towards each edge, feeding said powder layerthrough compacting rolls to compact said powder layer into metal strip,sintering the resulting compacted metal strip, cold rolling andannealing the compacted and sintered metal strip to producesubstantially dense, flat metal strip wider than about 1 inch andsubstantially free from frilling along the edges.

3. The method for producing substantially flat, dense metal strip by thedirect rolling of metal powder which comprises forming metal powderinto'an uncompacted layer at least about 1 inch wide and having a crosssectional thickness relatively greater towards the center thereof anddecreasing in thickness towards each edge by passing metal powderthrough a gap defined by a surface of a compacting roll and a spreaderwhich is fixed further from the said roll in the region of the rollcenter than at the roll edges, feeding said powder layer throughcompacting rolls to compact said powder layer into metal strip,sintering the resulting compacted metal strip, and subjecting thecompacted and sintered metal strip to a series of cold rollingoperations with intermediate annealing stages to produce substantiallydense, flat metal strip wider than about 1 inch and substantially freefrom frilling along the edges.

- References Cited in the file of this patent 7 Germany June 20, 1936

